I got this from someone else recently and thought that it was a neat little thing. I was projecting cloud storage to arrive shortly when Google opened up the Googledocs repository for 2Gb of online storage, but apparently these guys have been around for a year.
Dropbox is essentially 2Gb (basic free account) of online 'cloud' storage that you can access with a small tray application (which creates a junction to 'my documents') or directly with a browser. You can share nominated folders with other dropbox users or 'the public' via links, or just with other computers if you have a hatred of windows shares or a need for file access across the motherWAN.
This weekend I'll be playing with it and Junction (http://en.wikipedia.org/wiki/NTFS_junction_point) to try and dump my Steam save files in a location to share between my computers, and I'm going to have a crack at doing the same for Eve stuff.